Fertigation in citrus, a toolkit for sustainable quality production

Abstract

Techniques and managements of perennial fruits production are nowadays directed towards the need to conserve resources, energy and a commitment to the environment. In this sense, fertigation has risen as a valuable tool in recent years spreading around the world in major fruit belts. The million dollar question strikes why fertigation out-performs conventional basin method of irrigation carrying fertilizers. Citrus trees do not exhibit visible symptoms of water stress until most of the available soil moisture has been depleted. However, fruit set can be adversely affected at soil moisture depletion levels of only 40 to 50 percent, particularly from pre-bloom through June. Consequently, extensive research in the citrus production areas has led to the recommendation that water be applied at one-third depletion during January through June and at two-thirds depletion over the remainder of the year.Fertigation is an effective method of fertilizing in arid climates. Fertilizer levels in the soil are maintained at constant levels of 35–60 mg/kg throughout the irrigation period. Studies suggest that optimum nitrogen rate for mature Shamouti orange trees is about 170kg/ha/year. Higher nitrogen (N) rates increased yields but decreased external fruit quality by delaying peel color development and increasing peel thickness. However, juice quality, specifically total soluble solids, was not affected by nitrogen rate.A plant exposed to uniform regime of moisture and nutrient flow within rhizosphere zone has to spend much less energy than the growing conditions constantly changing over time. Fertigation, is thus, energy efficient as well. While addressing these concerns, however, the major concern emerges as orchard efficiency vis-a-vis FUE/WUE by adopting variable rate fertilizer application taking into consideration the spatial variability in soil properties in a time domain manner known as automated fertigation.This has led to an increase in both fertilizer use efficiency (FUE) and water use efficiency (WUE).